1. Technical Field
The present invention generally relates to a polishing apparatus (or system) useful in the fabrication and processing of semiconductor wafers. More particularly, the invention relates to a device and related method adapted to detect a malfunction related to a pad conditioner in the polishing apparatus.
This application claims the benefit of Korean Patent Application No. 10-2004-0071967, filed Sep. 9, 2004, the disclosure of which is hereby incorporated by reference in its entirety.
2. Discussion of Related Art
The typical sequence of processes used to manufacture semiconductor devices is a long and complicated one. Many individual semiconductor devices are manufactured on a single substrate. This substrate is usually provided in the form of a thin wafer of semiconductor material.
Over time, semiconductor devices have been formed a wafer with ever increasing height profiles. Increased height profiles result from higher integration densities and increased use of multi-layer structures. These interconnected multi-layer structures are generally formed layer by layer. To accomplish this, multiple planarization processes are performed prepare an upper surface of one structure or layer to receive another structure or layer.
A great variety of conventional, wafer planarization processes exist, including as examples, spin on glass (SOG), etch back, and reflow. Many of these processes include mechanical polishing and/or chemical polishing. Chemical and mechanical polishing has respective advantages and disadvantages. For example, a chemical polishing is preferred where a mechanical polishing might damage (e.g., grind) a delicate surface. However, it is often difficult to obtain a truly flat surface (e.g., an accurate topology) using only chemical polishing.
So, conventionally, some mix of mechanical polishing and chemical polishing has been required to accurately planarize a surface. In fact, the mutual presence of both chemical and mechanical polishing in conventional planarization processes is commonly referred to as Chemical-Mechanical-Polishing (CMP).
There are many types and variations of conventional CMP processes. Several examples are described here.
CMP is conducted at a polishing table. A wafer is attached to a polishing head using surface tension or vacuum pressure. A rotating polishing pad provided at the polishing table is forced into contact with the wafer under constant force. The pad rotation and the resulting forcible agitation polish the wafer. That is, using the weight of the polishing head and the applied force, the wafer surface and the polishing pad come into contact. The resulting plane of contact is typically washed with a slurry of polishing solution containing grinding particles and/or polishing agents (e.g., chemicals). The grinding slurry serves to remove polishing debris and grinding particles and supply polishing agents to the surface.
One example of a conventional polishing apparatus is found in U.S. Pat. No. 5,975,994.
A similar conventional polishing apparatus is illustrated on Figure (FIG.) 1. Within this apparatus, a wafer 12 is vacuum attached to a polishing head 10 which is attached to rotatable motor 26. A platen 20 attaching a polishing pad 16 is rotated in a direction contrary to the rotation direction of motor 26. Polishing head 10 is lowered until the facing surface of wafer 12 contacts polishing pad 16 while a slurry is supplied. A conditioning disc 24 driven by a motor 28 and attaching a conditioning pad 22 is typically provided as part of the foregoing polishing apparatus. Conditioning pad 22 is applied to polishing pad 16 in order to maintain a proper (e.g., planar) surface.
Polishing apparatuses like the one shown in FIG. 1 have been widely used in the industry for many years with excellent results. However, one notable exception to this excellent track record is reoccurring problems with a conditioning pad installed in opposition to the platen. Such conditioning pads have a frequent rate of malfunction. This frequent state of malfunction can cause larger problems, because if the conditioning pad is not regularly applied to the polishing pad (typically before and/or after each polishing process) problems arise, such as inadequate polishing rates and degraded polishing uniformity. These results threaten the reliability of semiconductor devices formed on the wafer.